1. Field of the Invention
The present invention relates generally to wake vortex avoidance, and, more particularly, to a self-contained, dynamic wake prediction and visualization system and architecture capable of accurately predicting wake vortices/turbulence and visualizing, via realistic representation, a no fly zone with the certainty that the wake hazard is wholly contained therein.
2. NomenclatureADS-BAutomatic Dependent Surveillance BroadcastAIMAeronautical Information ManualATAAir Transport AssociationATCAir Traffic ControlAVOSSAircraft Vortex Spacing SystemCTASCenter-TRACON Automation systemFAAFederal Aviation AdministrationFMSFlight Management SystemGPSGlobal Positioning SatelliteHUDHead-up DisplayIFRInstrument Flight RulesIMCInstrument Meteorological ConditionsINSInertial Navigation SystemsLAASLocal Area Augmentation SystemMFLAMEMultifunction Future LaserAtmospheric Measurement EquipmentMLWMaximum Landing WeightNASNational Airspace SystemNTSBNational Transportation Safety BoardOEWOperational Empty WeightRASSRadio Acoustic Sounding SystemTASTrue AirspeedTCASTraffic Collision Avoidance SystemTRACONTerminal Radar Approach ControlVASVortex Advisory SystemVFSVortex Forecast SystemVFRVisual Flight RulesVMCVisual Meteorological ConditionsWAASWide Area Augmentation System
3. Description of the Related Art
Over the coming decades, aviation operations are predicted to continue rising steadily, increasing the burden on already congested and constrained airports and terminal areas. Airspace congestion has led to delays that inconvenience passengers, cost the aviation industry hundreds of millions of dollars each year, and will eventually limit growth. FAA mandated separation distances between aircraft are a major challenge to alleviating airspace congestion. A major factor governing the safe, minimum separation distance is the hazard generated by the wake of a preceding aircraft. Unaware of the proximity of other traffic, en route aircraft may encounter wake turbulence generated by aircraft tens of miles ahead with serious or fatal consequences.
Currently, there is no means in place in the NAS that warns pilots of potential wake vortex encounters in an effective, reliable manner. The need for a warning system is especially critical during the approach and departure phases of flight when aircraft frequently follow in-trail. During VMC, pilots bear the responsibility to maintain a safe distance from other aircraft. This is commonly referred to as “see and avoid”. When pilots can see the other aircraft they can estimate the location of the wake, but the dissipation rate of the wake varies from aircraft to aircraft and it is difficult to make an accurate guess. For example, the wake of a Boeing 747 can linger up to 130 seconds in the right atmospheric conditions, whereas the wake of a Learjet may last only 40 seconds in the same conditions. During IMC, controllers are required to keep a certain horizontal and vertical separation between aircraft as the pilot may no longer be able to see the aircraft in front of them. This separation was established to give the atmosphere sufficient time to dissipate or carry the wake out of the path of the following aircraft. The wake is invisible under most atmospheric conditions. In IMC pilots rely entirely on ATC to keep them clear of the wake of the preceding aircraft.
Some general wake avoidance schemes have been proposed, including flight path limiting and multiple glide-path approaches. Unfortunately, these approaches do not convey wake information directly to the pilot, nor provide coverage outside the terminal area of the airport. Some efforts have also been made in altering the aerodynamic characteristics of the aircraft to alleviate wakes or reduce the wake-related hazards. However, while there has been some success in minimizing the wake hazards, the trade-off in modifying the aerodynamic characteristics has generally reduced the performance of the aircraft to an unacceptable level.
Prior art ground-based vortex prediction, detection, and forecasting systems include the Vortex Advisory System (VAS), the Vortex Forecast System (VFS), and the Aircraft Vortex Spacing System (AVOSS). In addition to being inefficient and costly, these prior art systems are only applicable at airports and terminal areas where appropriate equipment has been installed and, in some cases, only in close proximity to the runway.
The Airborne VFS is a proposal based on the research of the VFS. Using real time information about the aircraft, real time and predicted information about meteorological conditions, and real time modeling of vortex transportation and decay, the VFS predicts conditions under which the separation distance between aircraft may be safely reduced below the current standards. In order for the VFS to be implemented operationally, it must be integrated with other systems, such as the AVOSS, that can provide the data on aircraft state and environmental conditions. The Airborne VFS proposes displaying the above information on the cockpit windshield. Unfortunately, since the Airborne VFS is based on a complex set of algorithms and atmospheric measurements, it must be integrated with other ground-based systems and thus cannot be implemented for stand-alone airborne applications.
U.S. Pat. No. 4,137,764, “VORTEX ADVISORY SYSTEM,” issued to Hallock et al., discloses a technique for predicting the movement and life expectancy of vortices for the existing meteorological conditions and hence providing safe minimum separation between aircraft approaching a common runway. Hallock et al.'s invention utilizes a wind criterion to determine the required separation. The wind criterion refers to the winds measured, by a network of towers deployed around an airport, with respect to the landing aircraft. Measured wind parameters and safe aircraft separation are displayed to flight control personnel, i.e., ATC, on the ground. Under favorable wind conditions, ATC is given a green light to space arrival traffic closer than the FAA mandated IFR approach spacing.
U.S. Pat. No. 5,657,009, “SYSTEM FOR DETECTING AND VIEWING AIRCRAFT-HAZARDOUS INCIDENTS THAT MAY BE ENCOUNTERED BY AIRCRAFT LANDING OR TAKING-OFF,” issued to Gordon, discloses a system, comprised of a ground based system and an aircraft based system, for detecting and viewing aircraft hazardous incidents that may be encountered while landing or taking-off, i.e., in close proximity to an airport runway. These hazardous incidents include aircraft and meteorological phenomena such as microbursts, thunderstorms, tornadoes, and wake turbulence. The wake turbulence is detected by ground detection devices and then positionally and horizontally displayed to the pilot in relation to the flight path of the aircraft.
Another way to detect and measure wake turbulence created by aircraft, particularly jumbo jets landing and taking off on airport runways, is disclosed by Wang in U.S. Pat. No. 5,838,007, “OPTICAL SCINTILLOMETER WAKE VORTEX DETECTION SYSTEM.” Wang discloses an optical scintillometer to measure in real time atmospheric wake vortex turbulence intensity up to a distance of ten kilometers. Wang discovered that by measuring the fluctuation of turbulence, rather than the turbulence itself, and by measuring the fluctuation of wind, rather than the cross wind speed itself, meaningful measurements of rates of change of turbulence can be produced to indicate dangerous conditions over a time constant of one second or less.
U.S. Pat. No. 5,845,874, “SYSTEM AND METHOD FOR CREATING VISUAL IMAGES OF AIRCRAFT WAKE VORTICES,” issued to Beasley, discloses a method for creating a computer model of wake vortices based on characteristics of the aircraft that is generating them. Environmental and aircraft data are used to compute the position and orientation of the bounds of a wake vortex based on commonly known theoretical and empirical knowledge of wake vortices. The simulated wake vortex is displayed to air traffic controllers or pilots.
U.S. Pat. No. 6,177,888, “WAKE TURBULENCE WARNING AND CAUTION SYSTEM AND METHOD,” issued to Cabot et al. and assigned to the Boeing Company of Seattle, Wash., USA, discloses a wake turbulence warning and caution system that alerts a crew member to a potential conflict with the wake of another aircraft only when the system determines that intersection of the aircraft with the wake is about to occur within a predetermined amount of time. The wake tracking unit of the system assumes that the wake terminates at a predetermined distance behind the generating aircraft. In addition, the height and width of the wake volume are assumed to grow linearly with distance behind the aircraft. Cabot et al.'s invention, hereinafter referred to as “the Boeing system,” utilizes existing avionics components on larger aircraft and thus can be implemented relatively inexpensively. For example, relative positions of the aircraft and the wake can be displayed on a two-dimensional navigation map display, such as that used in connection with the TCAS aboard an aircraft.
U.S. published patent application Nos. 2002/0075171 A1, “SYSTEM AND METHOD FOR PREDICTING AND DISPLAYING WAKE VORTEX TURBULENCE” and 2002/0089432 A1, “VERTICAL SPEED INDICATOR AND TRAFFIC ALERT COLLISION AVOIDANCE SYSTEM,” hereinafter referred to as “the Honeywell system,” disclose a hardware implemented method for predicting a trajectory of wake vortex. With an electronic circuit, a current trajectory of a host aircraft is determined as well as whether the current trajectory of the host aircraft intersects the predicted wake vortex trajectory. The position and altitude of the wake generating aircraft, i.e., the intruder aircraft, is determined relative to a local airport. The wake vortex is determined as a function of the intruder aircraft type information such as weight class. The host aircraft determines the intruder aircraft's weight class, rather its actual weight. The Honeywell system relies on the Mode S function of TCAS to determine aircraft identification and, similar to the Boeing system, presents wake information on a two-dimensional TCAS display.
None of the aforementioned prior art systems and methods provides a self-contained, accurate, real-time prediction and three-dimensional visualization of the location and movement of the wake turbulence. More importantly, they do not teach or suggest modeling and visualizing a wake hazard zone with the certainty that the wake is located therein.